1. Technical Field
The invention relates to audio amplification. More particularly, the invention relates to a digital input switching audio power amplifier.
2. Description of the Prior Art
The current trend for audio information processing is to place most audio sources in the digital domain, rather than in the analog domain. That is, audio information is now usually stored in a digital format, instead of in an analog format.
Existing amplifier technology typically concentrates on efficiency. Such modern technology evolved from the primitive Class D amplifiers of the 1970s. Parallel developments in device technology have resulted in faster semiconductors and better topologies that allow the manufacture of lower distortion Class D, or "switching" audio amplifiers. However, these amplifiers have typically had an analog input only, and must incorporate feedback to compensate for distortion due to timing errors. Accordingly, digital input streams must first be converted to analog signal and then amplified with an analog Class D amplifier to create an efficient digital input amplifier.
One approach to processing a digital signal pursuant to audio amplification uses an external digital-to-analog converter (DAC) for input conversion (the post-DAC portion of such a system is manufactured by Linfinity Microelectronics, Inc. 11861 Western Avenue, Garden Grove, Calif. 92841). Such audio amplification systems require analog feedback to have reasonable performance characteristics. The mixed-signal nature of this topology is inherently expensive to produce.
Another approach to processing a digital signal pursuant to audio amplification uses a digital signal processor (DSP) and a field programmable gate array (FPGA) configured as a power DAC capable of driving a loudspeaker (such system is manufactured by Apogee Technology, Inc. 129 Morgan Drive, Norwood, Mass. 02062). This approach is complex and expensive due to the large signal processing requirement and lower integration level.
It would be advantageous to provide a low cost, high efficiency, low distortion audio amplifier for digital audio sources.